The present invention relates to an electromagnetic valve for switching flow passage by solenoid means.
In an electromagnetic valve of this type, in which flow passage is switched over by solenoid means, a valve member for opening and closing a valve seat in a flow passage of a fluid is generally held by a movable iron core in solenoid means, and when power to a coil is turned on, the movable iron core is drawn to a fixed iron core and the valve member is separated from the valve seat. When power is turned off, the movable iron is separated from the fixed iron core by resilient force of a return spring, and the valve member is attached on the valve seat.
In such an electromagnetic valve, when the movable iron core is drawn to the fixed iron core, the two iron cores collide against each other violently, and a contacting surfaces of the two iron cores tend to be worn out. In particular, in case switching is performed frequently or electromagnetic attracting force is high, the two iron cores are more likely to subject to wearing.
The above movable iron core is slidably inserted into an iron core provided in the solenoid means in normal case. When operated, it slides along inner wall of iron core hole, and the sliding causes the movable iron core and wall of iron core hole to wear. Because the iron hole is designed in such manner that it is continuous to a bobbin wound with coil and to a metal magnetic plate, which is a part of a magnetic frame enclosing the bobbin and is abutted to end surface of the bobbin, the movable iron core always slides along the metal magnetic plate, and the contacting portions of these components are very easily worn out.